SPAR supermarkets

Hello, I don't know if this is the right platform.. I have one complaint about one of the products sold under their brand by Spar, the full cream yogurtx6. I buy them regularly as they are very nice, but I never checked the weight. They have 100g printed on the container. I was needing 500g for a baking recipe, baking is precise you cannot improvise like in cooking, I assumed I had to have 5 x yogurts but to make sure I weight them and to my surprise they all were between 85 g and 87g so as a result I used 6! Further, I am spot checking them and all without exception weight 85g to87g, yet they are marked as 100g...This is a good way to save money without the knowledge of the consumer and in today's time where all products are excessively marked up to recover loses , it is sad that Spar has joined the crowd! I am normally very happy with Spar products and services :-(